F-16 VS F-15 WVR

Unread postPosted: 02 Jul 2009, 07:16
by eleanordriver
For the F-15 A/C I have read that the wing loading is lower than the F-16 under most circumstances. I have also read that the F-15 has a higher thrust-to-weight ratio under most circumstances. The body and control surfaces of an F-15 are larger, allowing airflow to be diverted for a higher turn rate. The overall surface of the bottom of the F-15 should allow it to fly at slower speeds, and the higher thrust to-weight ratio should allow a lower loss of altitude during a turn-battle in a dog-fight.

How is it that I have read about and seen videos of F-16s winning dog fights (in turn battles) against F-15s?

Shouldn't the F-15 be able to out-turn the F-16 if similarly loaded?

Is this based on the pilot's skill and ability to handle G forces?

RE: F-16 VS F-15 WVR

Unread postPosted: 02 Jul 2009, 17:16
by johnwill
Here are the factors you mention:
1. F-15 has lower wing loading.
2. F-15 has higher thrust to weight.
3. F-15 has larger body and control surfaces.

Here's why the F-16 can overcome those factors:

1. Nominal wing loading is not a direct indicator of manueverability. In most WVR encounters, the F-16 horizontal tail is strongly loaded up, providing additional lift. The angle of attack will be lower as a result. The F-15 tail is down loaded, meaning the wing and fuselage must provide additional lift. The angle of attack will be higher as a result.

2. Thrust to weight is not a good indicator of energy loss during turning fights. (Thrust - drag) to weight is a better indicator. F-16 lower AoA results in less drag, while the F-15 higher AoA results in more drag. So the F-16 has better (thrust - drag) to weight than the F-15 and maintains higher energy.

3. F-15 larger body and control surfaces compared to weight are no better than the F-16. F-16 fuselage lift is very high, as much as 40% of total lift.

Two other items are important to F-15 vs. F-16 WVR capability, g limit and leading edge flaps. F-16 g limit is significantly higher than F-15 and is automatically limited. That means the F-16 pilot can pull right to the limit without fear of breakiing anything, while the F-15 pilot must monitor his g to prevent over g (and AoA). The F-16 LEF provides optimum lift for all A0A, while the F-15 has no such device.

The F-15 is a wonderful fighter, but in WVR fights, the F-16 can handle it (in most circumstances).

RE: F-16 VS F-15 WVR

Unread postPosted: 02 Jul 2009, 22:43
by eleanordriver
I see, I thought that the F-15 was G limited for the pilot's sake. No wonder the F-16 is internationally recognized as such a great dog-fighter.
Thanks for your response.
I hope these advantages have been considered in the design of the F-35, increasing its WVR capabilities as well. Obviously they can't add LEFs to a stealth fighter (easily), but I would like to see what it can do first hand someday (the F-16 too).

Re: RE: F-16 VS F-15 WVR

Unread postPosted: 02 Jul 2009, 23:42
by johnwill
eleanordriver wrote:I hope these advantages have been considered in the design of the F-35, increasing its WVR capabilities as well. Obviously they can't add LEFs to a stealth fighter (easily), but I would like to see what it can do first hand someday (the F-16 too).


All fighters designed since the F-16 appeared have tried to emulate those characteristics in one way or another. You can bet the farm that LM designed the F-35 to be at least as good as the F-16 in WVR combat and a whole lot better in BVR.

The F-22 and F-35 both have LEF.

Concerning F-15 g limit, it, like most other fighters, does exactly as it was designed. Designers all over the world are able to design to meet the reqirements of the customer.

RE: Re: RE: F-16 VS F-15 WVR

Unread postPosted: 02 Jul 2009, 23:56
by sprstdlyscottsmn
what are the g- limits of an F-15? 9 G at half fuel only?

RE: Re: RE: F-16 VS F-15 WVR

Unread postPosted: 03 Jul 2009, 04:21
by johnwill
F-15 was designed as 7.33g at half fuel (I believe) in the early 70s. Could be different now.

Unread postPosted: 03 Jul 2009, 17:03
by bazdriver
F-15A non OWS : 7.33g at full air-to-air weight (OWS= Overload warning sytem)

F-15A and F-15C OWS equiped: 9g at full air-to-air weight

F-15 operationnal AOA envelope: 45 deg full air-to-air load wirhout external tanks.

F-16 operationnal AOA envelope: 28 deg air-to-air config.

Check SETP documents about High AOA and OOCF behaviour of F-16 and F-15

Unread postPosted: 06 Jul 2009, 14:00
by eleanordriver
"Check SETP documents about High AOA and OOCF behaviour of F-16 and F-15 "

Where?

Unread postPosted: 06 Jul 2009, 14:22
by outlaw162
http://208.77.90.112/whoglue/setpPaper/ ... ?view=1158

You may have to pay for it.

OL

(not to be confused with those child psychology sites)

Unread postPosted: 06 Jul 2009, 21:25
by eleanordriver
ok, thanks outlaw.

Unread postPosted: 06 Jul 2009, 22:00
by Pilotasso
Word is that Both planes are balanced at low altitudes with the 16 having a slight edge, however the F-15 beats the 16 hands down at higher altitudes.

Unread postPosted: 07 Jul 2009, 23:36
by Kryptid
I know that originally the F-15 had positive static stability. Have any more recent models been given negative static stability by, for example, moving the center gravity and modifying the flight control systems?

Unread postPosted: 24 Jul 2009, 03:49
by Des
If they are both carrying the helmet mounted cueing AIM-9X's then i suppose it will be whoever gets the first look.

Unread postPosted: 24 Jul 2009, 07:23
by F16guy
Pilotasso,

I'll have to say I don't agree. Maybe you need to define High altitude, (40+). Even then I've got to say the Viper holds its own in a dogfight up high. Having started maneuvering that high WVR the jets have what appears to be similar rates and turn radii, the Vipers' thrust(air-air configured) and low energy loss rate usually mean that both jets end up descending in a neutral fashion (if the set up was from high aspect) until the lower attitudes. I've never had an Eagle stay high and use the altitude against me or go where I could not, the multiple pilots I've fought in that jet always seemed to have as much difficulty turning an advantage up high as I had. That's my words anyway. Oh and for the Viper lovers on this forum, the Eagle is an outstanding jet with some awesome avionics with respect to the Viper. I'm glad that jet is on our side.

Des is right, First look and shot will usually result in the first kill, however, in todays' combat everything could go right for the blue pilot and he might still end up under a chute just like the guy he shot, since having the first shot does not mean it is exclusive and the other guy won't get a shot off in return before impact.

Unread postPosted: 24 Dec 2009, 14:30
by bazdriver
Johnwill, before getting into some comments, I will just say that I fully appreciate all your comments about the F-16. But I think you miss some knowledge about F-15 aerodynamics.


1. Nominal wing loading is not a direct indicator of manueverability. In most WVR encounters, the F-16 horizontal tail is strongly loaded up, providing additional lift. The angle of attack will be lower as a result. The F-15 tail is down loaded, meaning the wing and fuselage must provide additional lift. The angle of attack will be higher as a result.


As you know, the F-16 is only unstable below Mach 0.8/15 °AOA(whichever came first), above this values it is neutrally stable. The F-15 is statically stable at low speed. At high subsonic speed the position and shape of its intake ramps have a destabilizing effect and unload the tail by 10%. At supersonic speed their unloading effect is 30%. It's why without CAS the F-15 is very limited. The wing is optimized for maneuvering under high g, NOT for top speed(secret of which is on variable intakes ramps/engine optimization).Without getting into to much details an F-15 with CFT at an overall weight of 42000lbs needs only 12°AOA to load up to 9g at Mach 0.72.

2. Thrust to weight is not a good indicator of energy loss during turning fights. (Thrust - drag) to weight is a better indicator. F-16 lower AoA results in less drag, while the F-15 higher AoA results in more drag. So the F-16 has better (thrust - drag) to weight than the F-15 and maintains higher energy.

I mean you talk about Ps(specific excess thrust). Throughout the flight envelope the F-15 has higher values (particulary above Mach 1.5),largely compensating for the slight incrase in drag.

3. F-15 larger body and control surfaces compared to weight are no better than the F-16. F-16 fuselage lift is very high, as much as 40% of total lift.


Upper body lift of the F-15 is no less impressive. This, combined with the awesome power control of its tail surfaces( both vertical and horizontal) saved an Israeli F-15 years ago in a well known accident. Not sure an F-16 in similar circumstances would have survived.

Two other items are important to F-15 vs. F-16 WVR capability, g limit and leading edge flaps. F-16 g limit is significantly higher than F-15 and is automatically limited. That means the F-16 pilot can pull right to the limit without fear of breakiing anything, while the F-15 pilot must monitor his g to prevent over g (and AoA). The F-16 LEF provides optimum lift for all A0A, while the F-15 has no such device.


G limit advantage of the F-16 is only in a very very small part of the flight enveope.(though it can be decisive in some case). Full authority FCS has its advantages and drawbacks. It will take much more time and training to an F-15 driver to master the full flight envelope, no question about this, but it can give him the edge in some( but rare) conditions. You don'nt need to monitor the g or AOA, you just need to listen. OWS will provide you with cues(two tones beep rate) to not overstress your airplane. Now you can take F-15 flight manual from first page to last page, AOA limitations are provided only for specific cases:
- external tanks

- out of limits weight lateral asymmetry

- CAS-off operation or default(any axis)

- above 60°/s yaw rate

About LEF I would just say that F-15 wing is optimized for maneuvering( to the detriment of cruise drag). They are few available data about L/D concerning the two aircraft, but the only available show that F-16 has much higher L/D at low AOA/g combination, the F-15 wing closing the gap as you get to high AOA/g values. The F-15's wing is a masterpiece of engineering. Sukhoi and Tsagi tried to emulate it on the first T-10 prototype but never succeeded, reverting to LEF design(and successful)

Unread postPosted: 24 Dec 2009, 15:11
by bazdriver
Sorry but I just forget one or two things in my previous message. One is purely technical. The 12°AOA,9g Mach 0.72 is at sea level. Now I will say that I totally approve F-16guy comment. This is one of the reasons why the F-15/F-16 combination was so succesfull in the 1982 Lebanon conflict. The two aircrafts are so close in flight envelope that they can conduct cooperative attacks with impressive results.

Unread postPosted: 29 Dec 2009, 15:30
by johnwill
bazdriver,

Sorry to be late in responding, but I have been away for the Christmas holidays.

I agree that you and others could give me some good lessons on F-15 aero. That's why I was intentionally vague about it. I could do the same for you in regard to some F-16 characteristics. For example, the F-16 is unstable up to 0.92 mach, not 0.80. I guarantee it. And AoA has nothing to do with it.

The inlet effect is noted, but the F-15 tail is still down loaded at all positive g conditions, I believe. Also you say that the inlet effects are less at lower speeds, just where WVR usually happens, so as the fight progresses and speeds usually drop, the F-15 becomes more stable, not what you want.

So the F-15 Ps is better above 1.5 mach? Not a place where WVR normally happens, and we are talking about WVR.

The Isreali incident you mention is irrelavent to this discussion.

I have a question for you concerning OWS. When I first read of it 15 or 20 years ago, its purpose was to limit wing loads in high g rolls. Now from your comments it seems to protect the wing in symmetric turns as well. Is that true? I also question your earlier statement that the F-15 has a 9g limit at full air to air weight with OWS. Isn't it true that the OWS will give warning tones at less than 9g in some flight conditions? If so, then you cannot say the F-15 has full 9g capability. I am asking a question, not making a statement.

The F-15 wing is a nice design, but is optimized for only one thing - maneuverability. It reminds me of an F-16 wing with the LEF locked at about 8 degrees. An automatic LEF, which most if not all other modern fighters use, is clearly superior in its capability to handle many different conditions. Although not the first to have a LEF, the F-16 was the first to have an automatic maneuvering LEF.

I greatly respect your viewpoint and your opinions and would welcome more discussions. Obviously I am not a pilot, but have an engineer's perspective.

Unread postPosted: 29 Dec 2009, 18:31
by bazdriver
For example, the F-16 is unstable up to 0.92 mach, not 0.80.


Ok for me. The data came from an article in Flight International Magazine.


The inlet effect is noted, but the F-15 tail is still down loaded at all positive g conditions, I believe. Also you say that the inlet effects are less at lower speeds, just where WVR usually happens, so as the fight progresses and speeds usually drop, the F-15 becomes more stable, not what you want.


I was just puting the fact that trim drag of the horizontal tail is not as high has some might imagine.

I have a question for you concerning OWS. When I first read of it 15 or 20 years ago, its purpose was to limit wing loads in high g rolls. Now from your comments it seems to protect the wing in symmetric turns as well. Is that true? I also question your earlier statement that the F-15 has a 9g limit at full air to air weight with OWS. Isn't it true that the OWS will give warning tones at less than 9g in some flight conditions? If so, then you cannot say the F-15 has full 9g capability. I am asking a question, not making a statement.


The OWS was from the start intended for providing warning to the pilots that they are approaching g-limit condition whatever the type of maneuver. Those limits varies with speed and weight. The OWS constantly calculates allowable symmetrical load factor using:

a)aircraft gross weight derived from the production fuel quantity system and incremented by external stores data;and

b)a Mach Number derived from the production Air Data Computer

The allowable symmetrical load factor is then decremented by an amount proportional to lateral stick position to produce the total allowable load factor. Now when you approach to max allowable G-load(92%) you get a 2Hz tone in your headset and then a 10Hz(98%). So the F-15 is not a true continuous 9g machine like the F-16 at Design gross weight. It has a small part in the flight envelope where 9g capacity is not here(known as the "thumb-print" in the flight manual).

It's the reason I do the following comment in my previous post.
G limit advantage of the F-16 is only in a very very small part of the flight enveope.(though it can be decisive in some case).


About WVR consideration and Ps
I mean you talk about Ps(specific excess thrust). Throughout the flight envelope the F-15 has higher values


Now the two aircraft will preferably fight at speed above 375kts and use their high Ps values in vertical maneuvers to cut lower speed adversary trajectories. But that's a personnal point of view.

Unread postPosted: 11 Jan 2010, 10:58
by eleanordriver
Nice to see this discussion has continued, thanks for the info.

What about the Strike Eagle? If used in an Air-to-Air setup, with light weapons loading, would it be able to operate safely at higher G? I ask because the aircraft is structurally reinforced, which accounts for its much higher max payload.

Unread postPosted: 14 Jan 2010, 20:46
by bazdriver
eleanordriver wrote


--------------------------------------------------------------------------------

Nice to see this discussion has continued, thanks for the info.

What about the Strike Eagle? If used in an Air-to-Air setup, with light weapons loading, would it be able to operate safely at higher G? I ask because the aircraft is structurally reinforced, which accounts for its much higher max payload.


Remove the Lantirn pods, remove those CFT, and a (I insist) -229 equiped aircraft is the equal of a -220 equiped A to D aircraft in the A2A arena. About the G-limit, its advantage is that (due, as you said, to the beefed-up structure) it'not subject to the "thumbprint" 9g limitation of the A-D version. So it's really a full 9g aircraft(as the F-16) at design gross weight throughout the flight envelope.

Unread postPosted: 20 Jan 2010, 07:59
by eleanordriver
With the beefed up structure and more powerful engines, wouldn't producing more Strike Eagles be a good and cheap (relatively) suppliment to the force since the F-22 is going out of production due to bad press and the F-35 is going to be delayed. Strike Eagles could be an adaptable force if produced with the intention of being used as air-to-air fighters with equipment stripped off or Deep Strike aircraft when loaded.

Unread postPosted: 21 Jan 2010, 05:54
by sprstdlyscottsmn
Why strip the strike eagle? Would you rather take off with 1-3 gas bags that you are not allowed to drop and cause you to only gain the benefit of half the gas inside, or have the same amount of fuel as two and a half in a package that has less added drag then one?

Unread postPosted: 22 Jan 2010, 03:22
by psychmike
WOW. Thanks to Bazdriver and Johnwill for a fascinating exchange. Not being an expert in this area, I could only understand about 1/3 of what you were both discussing but I learned a lot. The fact that you were both respectful and collegial shows that you're both not only highly intelligent and experienced but people of good character as well. THIS is why I LOVE F-16.net!!!

Unread postPosted: 22 Jan 2010, 18:26
by bazdriver
Thanks Psychmike!
Why strip the strike eagle? Would you rather take off with 1-3 gas bags that you are not allowed to drop and cause you to only gain the benefit of half the gas inside, or have the same amount of fuel as two and a half in a package that has less added drag then one?


With the beefed up structure and more powerful engines, wouldn't producing more Strike Eagles be a good and cheap (relatively) suppliment to the force since the F-22 is going out of production due to bad press and the F-35 is going to be delayed.


I will not be long because the question of eleanordriver is calling an other topic. I will give my vote to sprstdlyscottsmn. Any F-15I driver will concede that it can not tangle with a Baz or Akef in the knife fight regime, but to get here, you have to defeat its weapons system. Now ,even in WVR, never forget that F-15I like F-18F have two pilots with each of them with DASH/JHMCS, that can independently track and slave a AIM-9X/Python 5 to two seperated targets,

Now concerning the USAF, even if I'm a true F-15 lover and considering it a more capable platform, I think they should preferably buy F-16 block50/52 or 60 if a stop gap mesure is needed. They are much less costly to operate in most missions.

Unread postPosted: 26 Jan 2010, 05:05
by sprstdlyscottsmn
bazdriver, forgive me for asking, but I can't seem to find what an Akef is. Can you help me out? And I certainly agree with you about the twin pilot issue, those extra eyes alone are worth the 500lbs of gas in a high threat environment. Does the Ra'am have better radar than the Baz?

Unread postPosted: 27 Jan 2010, 18:30
by bazdriver
sprstdlyscottsmn
Posted: Jan 26, 2010 - 05:05 AM

--------------------------------------------------------------------------------

bazdriver, forgive me for asking, but I can't seem to find what an Akef is. Can you help me out? And I certainly agree with you about the twin pilot issue, those extra eyes alone are worth the 500lbs of gas in a high threat environment. Does the Ra'am have better radar than the Baz?


Hello Sprstdlyscottsmn. Sorry to be late.

In Israeli Air Force

F-15A/B: Baz (Falcon)
F-15C/D: Akef(Buzzard)
F-15I: Ra'am (Thunder)


The radar. hmm. Actually F-15 most Baz and Akef are equipped with APG-63 nearly equivalent to APG-63 V(1), which in turn is better A2A than the APG-70 and is also equipping F-15K if I remember. But some specific modes are deleted in comparison to USAF one's. Maybe, a further upgrade can involve APG-63 V(3) (though certainly a degraded one) or an Elta alternative to both the Akef and Thunder.Maybe...(F-35 availability and price would be determinent).
Baz are too old in terms of economical value for a further upgrade of radar.

Unread postPosted: 29 Jan 2010, 00:45
by sprstdlyscottsmn
Okay, thanks, that clarifies a lot for me.